Milk Fat Globule Membrane Enhancement of Neurotransmitter Synthesis from Lactic Acid Bacteria
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Date
2023-12
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The Ohio State University
Abstract
Neurotransmitters like serotonin, dopamine, and gamma-amino butyric acid (GABA), are communication molecules known to improve mood and mental health. They can be produced in the gut and send signals to the brain via the gut-brain axis. This bidirectional link involves major body systems that influence physiological responses to the environment. To complement the host’s neurotransmitter production, probiotic lactic acid bacteria (LAB) also produce neurotransmitters. These bacteria are present in dairy foods along with the milk fat globule membrane (MFGM) which is a bioactive component of milk that influences brain and gut health. We hypothesized that MFGM can enhance neurotransmitter production from LAB. Therefore, the objectives of this work were to characterize neurotransmitter production of selected LAB and determine the influence of MFGM on production. Four LAB strains (Pediococcus acidilactici, Lactobacillus helveticus, Limosilactobacillus reuteri, and Lacticaseibacillus rhamnosus) were selected based on screening of probiotic characteristics and/or possession of neurotransmitter synthesis genes. All strains were cultured overnight before incubation with amino acid precursors (L-Trp, L-Phe, or L-Glu) for each neurotransmitter and MFGM. For serotonin and dopamine, cell-free supernatants were partially purified using a C18 column followed by vacuum evaporation and water resuspension. Serotonin was measured using Ehrlich’s reagent at A625. Dopamine was quantified using ferric chloride and potassium hexacyanoferrate at A735. For GABA, cell-free supernatants were concentrated using vacuum evaporation before mixing with GABase solution to measure absorbance at 340nm. Serotonin and dopamine were both produced by all strains, while GABA was not detected by any strain. Serotonin production was enhanced up to 5-fold with MFGM and dopamine was unchanged by MFGM. These findings lay the foundation to further explore how dairy foods containing probiotics influence human health.
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Keywords
Bioactive components of dairy milk, Gut-brain axis, Mental health